Abstract:

A method of detecting abnormal operation of a plasma process, includes:
(i) detecting a potential Vpp1 between an upper electrode and a lower
electrode disposed parallel to each other in a reaction camber at a time
T1 after the plasma process begins in the reaction chamber; (ii)
detecting a Vpp2 between the upper electrode and the lower electrode at a
time T2 after T1; (iii) comparing Vpp1 and Vpp2 to obtain an operation
value; and (iv) determining abnormal operation if the operation value is
within a predetermined range.

Claims:

1. A method of detecting abnormal operation of a plasma process,
comprising:detecting a potential Vpp1 between an upper electrode and a
lower electrode disposed parallel to each other in a reaction camber at a
time T1 after the plasma process begins in the reaction chamber;detecting
a Vpp2 between the upper electrode and the lower electrode at a time T2
after T1;comparing Vpp1 and Vpp2 to obtain an operation value;
anddetermining abnormal operation if the operation value is within a
predetermined range.

2. The method according to claim 1, wherein the plasma process is a
cleaning process.

3. The method according to claim 2, wherein the predetermined range of an
operation value satisfies Vpp2.gtoreq.Vpp1.

4. The method according to claim 1, wherein the plasma process is a film
deposition process.

5. The method according to claim 4, wherein the predetermined range of an
operation value satisfies |Vpp2-Vpp1|≧a threshold value.

6. The method according to claim 1, wherein T1 is at or near a midpoint of
the plasma process.

7. The method according to claim 1, wherein T2 is at or near an endpoint
of the plasma process.

8. The method according to claim 1, wherein the upper electrode is a
showerhead, and the lower electrode is a susceptor.

9. The method according to claim 2, wherein the upper electrode is a
showerhead, and the lower electrode is a susceptor, and the plasma
process is remote plasma cleaning, said method further comprising
applying an electric voltage between the upper electrode and the lower
electrode for detecting Vpp1 and Vpp2.

10. The method according to claim 1, wherein the reaction chamber is a
PECVD reaction chamber.

11. The method according to claim 1, further comprising stopping the
plasma process when the abnormal operation is detected.

12. The method according to claim 1, further comprising transmitting the
detected Vpp1 and Vpp2 to a host computer where the comparing step and
the determining step are performed.

13. The method according to claim 1, further comprising selecting T1 and
T2 before detecting Vpp1 and Vpp2, respectively, wherein T1 and T2 are
the only points of time for detecting a potential between the upper
electrode and the lower electrode for determining abnormal operation.

14. The method according to claim 1, which consists of the steps of
detecting Vpp1, detecting Vpp2, comparing Vpp1 and Vpp2, and determining
abnormal operation.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application is a divisional of U.S. patent application Ser. No.
11/134,774, filed May 20, 2005, the disclosure of which is herein
incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]This invention relates to a plasma processing apparatus used for
depositing films on semiconductor wafers, etc., and to a method to
diagnose cleaning processes.

[0004]2. Description of the Related Art

[0005]Chemical Vapor Deposition (hereinafter referred to as "CVD") is a
processing method widely used in the semiconductor industry. In a CVD
process, chemical reaction of various gases inside a reaction chamber
cause a film to be deposited on semiconductor wafer substrates. In order
to deposit a film on substrates at low temperature and high speed inside
the reaction chamber, a plasma gas can be generated in a deposition step.
This process is called "Plasma Enhanced Chemical Vapor Deposition"
(hereinafter referred to as "PECVD").

[0006]In a deposition process, films also deposit on the interior walls of
the reaction chamber and other parts inside the chamber, and cause
particles to generate. If these particles get onto substrates, they can
have significant negative effects on the semiconductor manufacturing
process that involves very minute components and structures. Therefore,
these contaminating particles must be removed.

[0007]For the above reason, the reaction chamber used in a PECVD process
must be regularly cleaned to remove the films deposited in the preceding
deposition process. Normally, this cleaning process is implemented by
flushing the reaction chamber with NF3 or other fluorine gas.

[0008]However, this cleaning process is not always implemented normally,
and cleaning sometimes occurs late or too early for various reasons (such
as when the films deposited inside the chamber are thicker or thinner
than normal). In this case, the cleaning process may not complete within
the specified time (under-cleaning) or the chamber may be cleaned
excessively (over-cleaning). In the event of under-cleaning, which
indicates insufficient cleaning, the unnecessary films deposited on the
interior walls of the reaction chamber, on the showerhead, etc., cannot
be thoroughly removed. The residual films will affect the subsequent film
deposition processes and reduce the properties of produced films.

[0009]To address this problem, a solution can be proposed in which the
cleaning step in the recipe is set long from the beginning. However, if
cleaning completes normally, a long cleaning step results in
over-cleaning and may damage the parts inside the reaction chamber. A
long cleaning step also prolongs the recipe execution time, which in turn
reduces the number of wafers that can be processed per unit time
(throughput). Furthermore, since fluorine gases used for cleaning the
reaction chamber are expensive, setting a long cleaning step can be a
costly exercise.

[0010]In view of the problems mentioned above, methods to automatically
detect an endpoint of an etching or cleaning process have been proposed,
including the one disclosed in Published Japanese Translation of PCT
International Patent Application No. 2003-521807.

[0011]This method detects an endpoint of etching or cleaning by
continuously and simultaneously monitoring at least one condition, but
preferably two or three processing conditions, being selected from: power
supply, forward RF power, RF reflected power, RF matching component, RF
peak-to-peak voltage/current and phase component, DC bias and chamber
pressure. In addition, this method determines an endpoint using two
processing conditions (first and second processing conditions).

[0012]In this case, the first processing condition is continuously
monitored and when an endpoint is detected under the first processing
condition, the other processing condition, or the second processing
condition, is used to confirm that the detected endpoint is correct, in
order to improve the accuracy of endpoint judgment. In other words,
whether the endpoint detected by the first processing condition is
correct or not is determined based on whether or not the result obtained
by the second processing condition corresponds to a predetermined value
or falls within a predetermined range. If the result obtained by the
second processing condition does not correspond to a predetermined value
or fall within a predetermined range, an "error flag" is set and an error
is recognized.

[0013]Under this technology, however, no "error flag" is issued under the
second processing condition if the etch rate or cleaning rate is low and
an endpoint is not detected under the first processing condition. As a
result, the process continues until it is stopped by an external means.
This leads to under-etching or under-cleaning. Even when the etch rate or
cleaning rate is normal, no "error flag" is issued under the second
processing condition if an endpoint is not detected under the first
processing condition for some other reason. As a result, the process also
continues until it is stopped by an external means. This leads to
over-etching or over-cleaning, which may result in damaged parts and
lower throughput.

[0014]If the various signals are monitored using control software, use of
an online system increases the loads on the host computer and apparatus
controller PC because monitor commands must be issued continuously.

[0015]Furthermore, the endpoint condition may not be the same for all film
types, so the first and second processing conditions must be
predetermined for each type of target film. As a result, the settings
must be changed every time the type of target film is changed.

SUMMARY OF THE INVENTION

[0016]The present invention was developed in light of the problems
explained above. It is the object of one embodiment of the present
invention to provide a technology to diagnose abnormal operation of a
cleaning process or film deposition process in an accurate and simple
manner by means of detecting abnormal condition occurring in the cleaning
process or film deposition process through discontinuous detections of
one type of signal.

[0017]It is the object of another embodiment of the present invention to
provide a technology to diagnose abnormal operation of a cleaning process
or film deposition process that is not limited to certain types of film
or that can be applied universally to films of multiple types.

[0018]It is the object of yet another embodiment of the present invention
to provide a technology to issue a warning and immediately stop the
cleaning process or wafer lot processing, when abnormal operation is
detected, so that no more defective wafers will be manufactured.

[0019]It is the object of yet another embodiment of the present invention
to provide a technology to diagnose abnormal operation that can be
applied in addition to a conventional technology by forcing virtually no
changes to a system that uses such conventional technology.

[0020]In one embodiment of the present invention that achieves one or more
of the objectives explained above, the voltage applied between the
electrodes in the reaction chamber is measured in a cleaning process or
film deposition process on a plasma processing apparatus. By comparing
the voltages measured at two chronological points (or three or more
noncontiguous or intermittent points depending on the specific
embodiment) during the target process, whether or not the cleaning
process or film deposition process was implemented normally is
determined. In one embodiment, a warning is issued and the cleaning
process or film deposition process and wafer lot processing are
immediately stopped, if a problem occurs, so that no more defective
wafers will be manufactured.

[0021]Here, the voltage applied between the electrodes in the reaction
chamber when plasma is enhanced in a cleaning process or film deposition
process is called "Vpp." Solid line A in FIG. 1 is an example of behavior
of Vpp during a normal cleaning process.

[0022]The behavior of Vpp sometimes draws a curve, as indicated by dotted
line B in FIG. 1, for some reason. Compared with the normal pattern
indicated by the solid line, the Vpp peak of the curve is clearly
shifted. Specifically, this indicates that the cleaning rate was low and
the cleaning process did not complete within the time shown in FIG. 1
(abnormal operation of the cleaning process).

[0023]In one embodiment, a plasma processing apparatus proposed by the
present invention measures Vpp voltages at two chronological points
during a cleaning step in a recipe when a problem of low cleaning rate
occurs, as indicated by the dotted line in FIG. 1, and uses the
relationship of the measured voltages to determine if the cleaning
process was implemented normally. If the cleaning process was not
implemented normally, the process is stopped immediately.

[0024]The above method allows for detection of abnormal operation of the
reaction chamber during a cleaning process and immediate stopping of the
process, so that no more defective wafers will be manufactured.

[0025]Since measurement is taken at two chronological, noncontiguous
points, the loads on the host computer and apparatus controller PC can be
reduced.

[0026]Since the judgment of whether or not a process was implemented
normally is determined only via comparison of measured Vpp voltages, the
control software can also be simplified.

[0027]Abnormal operation can also be detected in a film deposition process
by measuring Vpp, just like in a cleaning process, and the same controls
can be implemented.

[0028]For purposes of summarizing the invention and the advantages
achieved over the related art, certain objects and advantages of the
invention have been described above. Of course, it is to be understood
that not necessarily all such objects or advantages may be achieved in
accordance with any particular embodiment of the invention. Thus, for
example, those skilled in the art will recognize that the invention may
be embodied or carried out in a manner that achieves or optimizes one
advantage or group of advantages as taught herein without necessarily
achieving other objects or advantages as may be taught or suggested
herein.

[0029]Further aspects, features and advantages of this invention will
become apparent from the detailed description of the preferred
embodiments which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]These and other features of this invention will now be described
with reference to the drawings of preferred embodiments which are
intended to illustrate and not to limit the invention. The drawings are
oversimplified for illustrative purposes.

[0031]FIG. 1 is a graph showing a typical behavior of Vpp voltage during a
cleaning process on a plasma processing apparatus and a behavior of Vpp
voltage when the reaction chamber is abnormal.

[0032]FIG. 2 is a flow chart showing the function to detect abnormal
operation during a cleaning process on a plasma processing apparatus in
one embodiment of the present invention.

[0033]FIG. 3 is a drawing showing the configuration of a plasma processing
apparatus used in one embodiment of the present invention.

[0034]FIG. 4 is a graph showing a typical behavior of Vpp voltage during a
deposition process on a plasma processing apparatus and a behavior of Vpp
voltage when the reaction chamber is abnormal.

[0035]FIG. 5 is a flow chart showing the function to detect abnormal
operation during a deposition process on a plasma processing apparatus in
one embodiment of the present invention.

[0036]FIG. 6 is a schematic drawing of a control system of a plasma
processing apparatus used in one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0037]The present invention includes, but is not limited to, the following
embodiments which can achieve one or more of the objects described above:

[0038]A method of detecting abnormal operation of a plasma process
comprises: (i) detecting a potential Vpp1 between an upper electrode and
a lower electrode disposed parallel to each other in a reaction camber at
a time T1 after the plasma process begins in the reaction chamber; (ii)
detecting a Vpp2 between the upper electrode and the lower electrode at a
time T2 after T1; (iii) comparing Vpp1 and Vpp2 to obtain an operation
value; and (iv) determining abnormal operation if the operation value is
within a predetermined range.

[0039]The above embodiment can further include the following embodiments:

[0040]The plasma process may be a cleaning process. Inner surfaces of the
reaction chamber are exposed to a plasma during film formation, and
unwanted accumulation of particles occurs thereon, especially on a
surface of the upper electrode. The accumulated particles are removed
through the cleaning process. The cleaning of an surface of the upper
electrode is particularly important with respect to quality of deposited
films. In an embodiment, by applying an electric voltage between the
upper electrode and the lower electrode and measuring Vpp, it is possible
to determine progress of the cleaning especially with respect to the
surface of the upper electrode.

[0041]As explained above, an example of behavior of Vpp during cleaning is
indicated in FIG. 1. In the beginning of cleaning, the upper electrode
surface is covered with a deposited insulation film, and Vpp is low. As
cleaning progresses, the insulation film is being removed from its
outmost surface, and Vpp increases. The thickness of the insulation film
is getting lower. Because the plasma density (in in-situ cleaning) or the
gas (i.e., radical) density (in remote plasma cleaning) near a periphery
of the upper electrode is lower than its center, the etch rate at the
center is greater than that at the periphery. When the insulation film is
getting thinner and then removed at the center, Vpp reaches a highest
point (a peak). Thereafter, the removal of the insulation film spreads
from the center toward the periphery, and Vpp decreases. When the
insulation film is completely removed, Vpp becomes stable. Note that the
above theory is tentative and is not intended to limit the present
invention.

[0042]If the etch rate is low for some reasons such as unanticipated
thickness of a deposited film, the peak is shifted, i.e., the cleaning
may not be complete within a predetermined time (T). Thus, by comparing
Vpps before and after the peak, it is possible to determine whether the
cleaning process operation is normal or abnormal. In an embodiment, T1 is
at or near a midpoint of the cleaning process, which is time "m", and T2
is at or near an endpoint of the cleaning process, which is time "T-n".
In FIG. 1, Vpp at time "m" is Va (Vpp1), and Vpp at time "T-n" is Vb
(Vpp2).

[0043]In the above, in an embodiment, if Vpp2<Vpp1, it can be
determined that the cleaning operation is normal, whereas if
Vpp2≧Vpp1, it can be determined that the cleaning operation is
abnormal. T, m, and n may be predetermined through experiments. In an
embodiment, n is about 0% to about 20% of T (in another embodiment about
5% to about 15% of T) which corresponds to a second stable (plateau)
value of Vpp. Alternatively, in an embodiment, the absolute value of a
difference between Vpp2 and Vpp1 (|Vpp2-Vpp1|) can be used to determine
the operation condition. For example, if |Vpp2-Vpp1|≦a threshold
value, the operation can be determined to be abnormal. The threshold
value can be predetermined through experiment. In another embodiment, a
ratio of Vpp2 to Vpp1 (Vpp2/Vpp1) can be used to determine the operation
condition.

[0044]The above-explained behavior of Vpp during cleaning can be common to
various types of insulation films deposited on the upper electrode
surface. Thus, software which is programmed to execute the above
determination procedures can be used universally.

[0045]In the above, in an embodiment, the upper electrode is a showerhead,
and the lower electrode is a susceptor, and the cleaning process is
remote plasma cleaning. Conventionally, during remote plasma cleaning, no
electric voltage is applied between the upper electrode and the lower
electrode in order to avoid damage to the upper electrode surface. In an
embodiment, even during remote plasma cleaning, an electric voltage is
applied between the upper electrode and the lower electrode for detecting
Vpp1 and Vpp2. If the cleaning is in situ cleaning, the electric voltage
applied between the upper electrode and the lower electrode for cleaning
can also be utilized for the purposes of detection of abnormal operation.
In an embodiment, the upper electrode and the lower electrode can be
additionally provided in the reaction chamber which are not used for film
deposition or cleaning but used for detection of abnormal operation.

[0046]In an embodiment, an electric voltage applied between the upper
electrode and the lower electrode may be in the range of about 500
W/m2 (of the upper electrode surface) to about 2000 W/m2,
preferably about 800 W/m2 to about 1500 W/cm2. In an
embodiment, the distance between the upper electrode and the lower
electrode may be in the range of about 5 mm to about 30 mm, preferably
about 10 mm to about 25 mm. The above-described principle can be applied
to any types of reaction chamber which involves plasma CVD.

[0047]Further, in an embodiment, more than two Vpp detecting points (the
above two plus one or two or more additional points) can be selected as
long as Vpp is not continuously measured. By detecting Vpp
intermittently, a system load can be minimized. Except for the time of
detecting Vpp, a timer can be the only unit activated. Other functions
need not be activated until they are called by the timer.

[0048]In another embodiment, the plasma process is a film deposition
process. The above-described principle of detecting abnormal operation
can be applied to a film deposition process. FIG. 4 shows an example of
behavior of Vpp during a film deposition process. In FIG. 4, Vpp is a
potential between the upper electrode and the lower electrode on which a
substrate is placed. In the beginning of film deposition, Vpp quickly
increases by analogue response and reaches a highest point (peak) due to
residual effect. Thereafter, Vpp drops and becomes stable. If the
operation is abnormal for some reasons such as abnormal plasma discharge
during deposition, Vpp drops near the endpoint of a predetermined time
period (T). Thus, by comparing Vpps before and after the drop, it is
possible to determine whether the film deposition process operation is
normal or abnormal. In an embodiment, T1 is at or near a midpoint of the
film deposition process, which is time "m", and T2 is at or near an
endpoint of the film deposition process, which is time "T-n". In FIG. 4,
Vpp at time "m" is Va (Vpp1), and Vpp at time "T-n" is Vb (Vpp2).

[0049]In the above, in an embodiment, if Vpp2≈Vpp1 (≈
means approximately or nearly the same in practical sense, allowing
ordinary deviations such as a difference caused by electric noise), it
can be determined that the film deposition operation is normal, whereas
if Vpp2<Vpp1, it can be determined that the film deposition operation
is abnormal. In an embodiment, the absolute value of a difference between
Vpp2 and Vpp1 (|Vpp2-Vpp1|) can be used to determine the operation
condition. For example, if |Vpp2-Vpp1|≧a threshold value, the
operation can be determined to be abnormal. The threshold value can be
predetermined through experiment. T, m, and n may be predetermined
through experiments. Alternatively, in an embodiment, a ratio of Vpp2 to
Vpp1 (Vpp2/Vpp1) can be used to determine the operation condition. An
electric voltage applied between the upper electrode and the lower
electrode for film deposition can also be used for detecting abnormal
operation; otherwise, the aforesaid electric voltage used for detecting
abnormal operation of cleaning can be used.

[0050]The above-explained behavior of Vpp during film deposition can be
common to various types of films deposited on a substrate. Thus, software
which is programmed to execute the above determination procedures can be
used universally.

[0051]In an embodiment, regardless of whether the plasma process is
cleaning or film deposition, the method may further comprise stopping the
plasma process when the abnormal operation is detected. It can be
accomplished by transmitting a signal to a host computer which operates
the plasma process when software determines abnormal operation. The
software can be installed separately from the host computer.
Alternatively, abnormal operation can also be determined by the host
computer.

[0052]FIG. 6 is a schematic drawing showing an embodiment of a control
system for a cluster type plasma CVD apparatus. In this figure, Slaves #1
to #5 are CPU boards for controlling each elements. Slave #1 to #3 are
installed for Reactors #1 to #3, Slave #4 is installed for an atmospheric
robot, and Slave #5 is installed for a vacuum robot in a wafer
transferring section. V is a Vpp detection unit (see FIG. 3 which will be
explained later). The Vs are connected to Slaves #1 to #3, respectively.
iTron is a CPU board of a main controller which controls all plasma
operation (e.g., recipe operation control) including cleaning and film
deposition. De is software for detecting abnormal operation based on Vpp
and stopping the abnormal operation through the iTron. De can control
both cleaning and film deposition. MMI PC is a PC for a man-machine
interface which is connected to a host computer. OS9 is a CPU board for
communication with the MMI PC. T1, T2, and a threshold for |Vpp2-Vpp1|,
for example, can be set and inputted using the MMI PC. In this figure,
the De is installed in the iTron, but De can be installed as an addition
to the host computer. Thus, controlling the abnormal operation detection
system does not substantially reduce the capacity of the main computer.
In this figure, the elements enclosed by the dotted line may constitute a
plasma CVD system which is connectable to a host computer of a user. In
the above, "connection" may include physical, electrical, functional,
direct, or indirect connection depending on the individual application.

[0053]In another aspect, the present invention provides a plasma CVD
apparatus comprising: (i) a reaction chamber for plasma CVD provide with
an upper electrode and a lower electrode disposed parallel to each other;
and (ii) a system for detecting abnormal operation of a plasma process in
the reaction chamber, said system being programmed to: (a) detect a
potential Vpp1 between the upper electrode and the lower electrode at a
time T1 after the plasma process begins in the reaction chamber; (b)
detect a Vpp2 between the upper electrode and the lower electrode at a
time T2 after T1; (c) compare Vpp1 and Vpp2 to obtain an operation value;
and (d) determine abnormal operation if the operation value is within a
predetermined range. The above mentioned elements with regard to the
methods can equally be applied to the apparatuses.

[0054]In all of the aforesaid embodiments including the methods and the
apparatuses, any element used in an embodiment can interchangeably be
used in another embodiment unless such a replacement is not feasible or
causes adverse effect.

[0055]FIGS. 2 and 3 illustrate a sample cleaning control process on a
plasma processing apparatus used in some embodiments of the present
invention. It should be noted, however, that the present invention is not
at all limited to these drawings and embodiments.

[0056]In FIG. 2, the control process comprises the 10 steps explained
below. The process starts in step 1, and whether the currently executed
portion of the recipe is a cleaning step or not is determined in step 2.
Here, it is assumed that the recipe contains software flags that are used
to identify special steps such as deposition and cleaning, wherein each
flag is set (a variable turns "ON") when the corresponding step is
started. If the cleaning step flag is not yet set in step 2, the software
program does not proceed to the subsequent steps and continues to wait
for the flag to be set. If the flag is already set, the software program
proceeds to step 3. In step 3, a timer is started to measure predefined
periods of m seconds and n seconds. Here, the specified values of m and n
may be typical periods that are determined by experimental data. In step
4, whether m seconds have elapsed or not on the timer is determined. If m
seconds have not yet elapsed, the software program stays in step 4 until
m seconds elapse. Once m seconds have elapsed, the software program
proceeds to step 5 and assigns the Vpp voltage at that point to variable
Va.

[0057]Here, reading of Vpp voltage into the control software can be
implemented using an apparatus of the configuration shown in FIG. 3, for
example. FIG. 3 is explained later on. Next, in step 6 the voltage at n
seconds from the endpoint of the cleaning step is read, in order to
determine whether (T-n) seconds have elapsed or not on the timer started
in step 3. Here, T is the step time of the cleaning step in the recipe.
If (T-n) seconds have not yet elapsed, the software program stays in step
6 until (T-n) seconds elapse. Once (T-n) seconds have elapsed, the
software program proceeds to step 7 and assigns the Vpp voltage at that
point to variable Vb. Next, in step 8 the software program compares Va
and Vb. If Va>Vb, the software program proceeds to the final step, or
step 10, and ends the control process. If Va≦Vb, the software
program determines that the cleaning rate is low and proceeds to step 9,
in which it issues a warning (alarm) and ends the recipe and wafer lot
processing. Thereafter, the software program proceeds to step 10 and ends
the control process. This control process is a subroutine process called
from a main control process of the plasma processing apparatus. The start
step of this control process, or step 1, should ideally be called when a
recipe process is started by the main control.

[0058]FIG. 3 is an example of configuration of plasma processing
apparatuses used in one embodiment of the present invention. An AC
voltage (1) is applied on an upper electrode (3) in a reaction chamber
(2) at a specified frequency. A lower electrode (4) is connected to
ground. The actual voltage applied between the electrodes is converted to
a digital signal via an analog-digital converter (5) and read into
control software (6). Although this configuration assumes that the upper
and lower electrodes (3, 4) in the reaction chamber (2) are parallel
plate electrodes, the present invention is not at all limited to this
electrode specification.

[0059]The above explained how abnormal operation of a cleaning process can
be detected based on the present invention, but this method can also be
applied to a deposition process. FIG. 4 shows a typical behavior of Vpp
voltage during deposition (the present invention is not at all limited to
this figure). Solid line C in the graph indicates the behavior of Vpp
voltage during a normal deposition process. Here, the voltage behavior
indicated by dotted line D in FIG. 4 sometimes occurs for some reason
(abnormal operation of the deposition process). In this case, the same
control flow chart in FIG. 2 can be used, with "Cleaning Step" in step 2
changed to "Deposition Step" and "Va>Vb" in the judgment algorithm in
step 8 changed to "|Va-Vb|<Threshold" (to determine whether the
absolute value of a difference between Va and Vb is smaller than a
threshold). Here, the threshold is an allowable limit of error in voltage
as determined by experimental data. A control flow chart for this
deposition process is given in FIG. 5. Here, all steps are the same as
those in the flow shown in FIG. 2, except for step 8.

[0060]To give you an example, Va and Vb in a cleaning process take 180 [V]
and 170 [V], respectively, when the process is normal, and take 180 [V]
and 200 [V], respectively, when the process is abnormal. In the case of a
deposition process, both Va and Vb take 260 [V] when the process is
normal, but they take 260 [V] and 250 [V], respectively, when the process
is abnormal.

[0061]Based on the above, whether or not a cleaning process was
implemented normally in a cleaning step during a recipe process on a
plasma processing apparatus can be determined by measuring Vpp voltages
at given two chronological points during the step and then comparing the
measured voltages. If the cleaning process was not implemented normally,
immediately a warning is issued and the recipe process and wafer lot
processing are stopped, so that no more defective wafers will be
manufactured. The apparatus can be inspected and serviced to identify the
problem, which can then be corrected to restore a normal condition.

[0062]The present invention not only applies to a cleaning step in a
recipe process, but it can also be applied to a deposition step in a
recipe process, wherein abnormal operation of the reaction chamber can
also be detected and the wafer lot processing can be stopped, as already
described above.

[0063]In the aforementioned embodiments, examples of diagnosing and
stopping cleaning and deposition processes on a plasma processing
apparatus by using the apparatus alone were explained. In actual
manufacturing lines, however, a semiconductor manufacturing apparatus is
often connected to a host computer. If this is the case, the judgment
processes shown in FIGS. 2 and 5 can be implemented on the host computer,
not by the apparatus control software. In this case, A-D converted Va and
Vb values are transmitted to the host computer, and the host computer
compares the Va and Vb values based on a set of judgment criteria stored
in the host computer and, if necessary, transfers a stop command to the
plasma processing apparatus. Here, the plasma processing apparatus itself
does not require any judgment function, and it only needs to provide a
communication environment that enables transmission of Vpp voltages to
the host computer.

[0064]The present invention is applicable either to a remote plasma
process where F radicals for cleaning gas are generated in a separate
unit and then introduced to the reaction chamber, or to an in-situ
process where F radicals are generated inside the reaction chamber.

[0065]In one embodiment explained above, the electrodes (3, 4) in the
reaction chamber (2) were assumed to be parallel plate electrodes.
However, the present invention is not at all limited to semiconductor
manufacturing apparatuses using parallel plate electrodes. Instead, it
can be applied to semiconductor manufacturing apparatuses that use
high-density plasma (HDP) or inductively coupled plasma (ICP), with
parallel plate electrodes for diagnosis attached in the reaction chamber.

[0066]From the above, a plasma processing apparatus that, according to the
present invention, compares the Vpp voltages at two chronological points
measured during a cleaning process and detects abnormal operation of the
reaction chamber is able to quickly detect abnormal operation of the
apparatus during processing and stop the processing so that no more
defective wafers will be manufactured. The apparatus can then be
inspected and serviced to resolve the problem.

[0067]The present invention includes the above mentioned embodiments and
other various embodiments including the following:

[0068]1) A plasma processing apparatus comprising software that detects
abnormal operation during a semiconductor wafer manufacturing process,
said software detecting abnormal operation of the reaction chamber by
comparing the voltages between electrodes at given two chronological
points measured during a cleaning process.

[0069]2) The plasma processing apparatus according to 1) above, wherein
the software detects an abnormal operation of the reaction chamber by
comparing the voltages between electrodes at given two chronological
points measured during the cleaning process, and stops the cleaning
process.

[0070]3) A plasma processing apparatus comprising software that detects
abnormal operation during a semiconductor wafer manufacturing process,
said software detecting abnormal operation of the reaction chamber during
a deposition process.

[0071]4) The plasma processing apparatus according to 3) above, wherein
the software detects abnormal operation of the reaction chamber based on
a change in the voltage between electrodes during the deposition process.

[0072]5) The plasma processing apparatus according to 3) above, wherein
the software detects abnormal operation of the reaction chamber by
comparing the voltages between electrodes at given two chronological
points measured during the deposition process.

[0073]6) The plasma processing apparatus according to 1) above, wherein
the software detects an abnormal operation of the reaction chamber by
comparing the voltages between electrodes at given two chronological
points measured during the deposition process, and stops the deposition
process.

[0074]7) The plasma processing apparatus according to 1) above, said
apparatus transferring to a host computer the voltages between electrodes
at given two chronological points measured during a cleaning step in a
semiconductor wafer manufacturing process.

[0075]8) The plasma processing apparatus according to 3) above, said
apparatus transferring to a host computer the voltages between electrodes
at given two chronological points measured during a deposition step in a
semiconductor wafer manufacturing process.

[0076]It will be understood by those of skill in the art that numerous and
various modifications can be made without departing from the spirit of
the present invention. Therefore, it should be clearly understood that
the forms of the present invention are illustrative only and are not
intended to limit the scope of the present invention.